1. Field of the Invention
The invention relates to a waste gas system for bioreactors with a hydrophobic sterile filter, arranged at the end, and a heat exchanger which protects the sterile filter in a particular manner against blocking by liquid media.
2. Description of the Related Art
When gas is introduced into a bioreactor, it takes up liquid vapors as it flows through a liquid medium, which liquid vapors would be entrained out in an undesired manner during uncontrolled exit from the bioreactor. The same effect would occur in biotechnological processes, where gases are formed as metabolic products and removed from the bioreactor. In order to avoid contamination, the opening in a bioreactor is usually provided with a sterile filter for gas removal purposes. According to the unpublished patent application DE 10 2008 025 968.3 by the applicant, the use of a condenser located in the gas outflow duct under turbulent flow of the waste gas is intended to prevent the sterile filter from being blocked by condensing liquids and the waste gases from entraining out some of the liquid culture medium. It is a disadvantage that owing to the turbulent flow a pronounced reduction in pressure occurs in the gas outflow duct. As a result, the bioreactors should be operated at relatively high pressures in the gas chamber, which is undesired for some reaction processes and in particular for such bioreactors composed of flexible plastic bags due to the risk of the occurrence of leakages. There is also the risk that liquid droplets will be entrained up to the sterile filter or will be precipitated in it and block it.
U.S. Pat. No. 5,443,985 A discloses a bioreactor having a vessel, which has at its upper end, in the vertical direction, a gas outflow duct for discharging gas. A water-cooled condenser is arranged between the vessel and a waste gas filter. The inside wall surrounding the gas outflow duct forms the condensation surface of the condenser. It is a disadvantage in this case that, if the gas throughput is too great, at least partial blocking of the waste air filter by condensate occurs. This is not even prevented if a relatively long condenser is used for cooling the waste gases. If the waste gas filter were to become too blocked, the introduction of gas and thus the culture process would have to be stopped.
U.S. Pat. No. 6,133,021 A likewise discloses a bioreactor having a water-cooled condenser in the gas outflow duct, which has the disadvantage that without a filter the waste gas escapes into the surroundings and the bioreactor is not protected by way of a sterile barrier.
Furthermore, DD 260 837 A3 discloses a fermenter having a vessel having a gas outflow duct for discharging gas. The opening of the gas outflow duct toward the surroundings is provided with a waste air filter (not described in more detail). The waste air flows either through a waste air condenser and the condensate which has formed drops back into the fermenter or it flows through a waste air cooler and the condensate collects in a condensate vessel. This waste gas system also has the above-mentioned disadvantages and is not suitable for a bioreactor having a hydrophobic sterile filter as a waste gas filter.
It is therefore an object of the present invention to propose an effective waste gas system for bioreactors which ensures a high degree of reliability during operation of the bioreactor.